(1) Field of the Invention
The present invention relates to the field of thermal transfer printing, more particularly wherein a yellow pattern or images are printed onto an acceptable sheet.
The present invention can be applied to the thermal transfer printing process of synthetic fibers and thermal transfer type recording systems, viz., information recording means, and it can provide various good color effects such as color fastness against light and enables the production of vividly colored images.
(2) Description of the Prior Art
Known yellow dyestuffs for heat transfer printing (Japanese Patent Publication No. 5029/1979) are styryl dyestuffs represented by the formula (2) ##STR2## pyrazole dyestuffs (reference literature: Japanese Patent Laid-open Nos. 139869/1976 and 10778/1978) represented by the formalae (3) and (4) ##STR3## pyridone dyestuffs (Japanese Patent Laid-open Publication No. 23782/1979) represented by the formula (5) ##STR4## and other dyestuffs.
Furthermore, as the coloring material for recording information, there has been suggested the utilization of Color Index Disperse Yellow 54 represented by formula (6): ##STR5##
Disclosed by the inventors of the present application (Japanese Patent Laid-open Publication Nos. 12393/198767 and 12394/1986) are pyrasolone and pyrazole dyestuffs represented by the formulae (7) and (8): ##STR6## wherein R.sup.1 is lower alkyl and R.sup.2 is lower alkyl or lower alkoxy and ##STR7##
When a yellow coloring material is used on synthetic fibers or record papers in accordance with a heat transfer system, important criteria of its quality are various color factors such as color fastness against light and color value. The color fastness factors and color value of the above-mentioned known coloring materials are poor. In addition, the color tones of these coloring materials are also not vivid.